Genale-Dawa III multipurpose hydropower project also called GD-3 is a 254MW hydroelectric power project situated in the Genale-Dawa River Basin in southeast Ethiopia. The GD-3 project took nine years for completion and was inaugurated in the first quarter of 2020.
Owned and operated by the Ethiopian Government, the project was developed by China Gezhouba Group, a member of China Energy Engineering Group.
The hydropower project will generate power and the dam will be used as a water reserve to serve the water demands of the landlocked country during the crisis. It will also supply water for irrigation of 15,000 hectares under a project named Lower Genale Irrigation Development Project.
Genale-Dawa III multipurpose hydropower project make-up
The Genale-Dawa III multipurpose hydropower project comprises of a concrete faced rock fill dam and an underground powerhouse. Based on the estimated sedimentation level, the project will have a lifetime of more than 1,000 years.
The dam site is located in a low seismic hazard area of class I. The dam is 110m high, 456m wide and 450m long. It is made with groutable and non-erodible rock and has a volume of 3.2 million cubic metres (mm3). At the full capacity, the dam can store up to 2,570mm3 of water. It has a catchment area of 10,445km2 and a fill volume of 890,000m3.
The dam spillway is an open chute type with an ogee weir crest and three radial spillway gates.
Genale-Dawa III powerhouse details
The underground powerhouse is installed with three vertical Francis turbine generators with a capacity of 84.7MW each. It is housed within an underground cavern measuring 60m-long, 20m-wide and 41m deep and also includes auxiliary equipment.
A 12.4km long, 8.1m diameter headrace tunnel carries water from the dam through a 188m deep steel-lined vertical shaft to a three-pronged manifold. The manifold feeds the water to the turbine inlet valves of the three turbines housed in the powerhouse. A 820m long tailrace tunnel and a 480m long open channel returns the water back to the river.
A transformer cavern is located downstream of the powerhouse and includes three step-up transformers. The electricity generated is transferred from the transformers to a 230kV/400kV switchyard located above ground through a 500m long cable tunnel.
Genale-Dawa III transmission infrastructure
The electricity generated by the Genale-Dawa III power plant is transmitted by 295km-long 400kV and 230kV transmission lines to the Mega substation, which will connect to the Ethiopian main grid.
The project was connected to the Ethiopian grid in February 2020.
The Genale-Dawa III project was constructed with a total investment of £352.7 ($451m). More than 80% of the investment was financed through loans and grants provided by various entities.
The project was majorly financed by EXIM Bank of China, which provided £254.85 ($326m) for the project, while the Ethiopian Government invested approximately £53m ($68m).
Stantec, a US-based company that provides integrated design services, was contracted for providing consulting services, design, planning, and construction management of the Genale-Dawa III project.
The feasibility study for the project was conducted by Lahmeyer International, a Germany-based engineering company and Yeshi-Ber Consult, an Ethiopia-based consulting firm.
TUNNELPRO, an Italy-based supplier of tunnel boring machines (TBM), provided the TBM for excavation of the headrace tunnel.
Genale hydropower projects
The Genale-Dawa Basin will have two more hydropower projects named GD-5 and GD-6 that are currently in the proposal stage. All the Genale-Dawa power projects are collectively named as Genale Hydropower Projects.
The GD-5 and GD-6 power projects will be located some kilometres parallel and adjacent to each other approximately 700km southeast of Addis Ababa.
GD-5 will be a 100MW facility, located roughly in the middle of GD-3 and GD-6. GD-6 will have a capacity of 250MW and comprise of two vertical generators of Francis turbines.